Remarkable catalytic properties of hierarchical zeolite-Beta in epoxide rearrangement reactions

• Hierarchical Beta zeolites and hybrid ordered zeolitic–mesoporous materials.
• Additional porosity favoured the accessibility of the reactants to the acid sites.
• Modified acidity respect to conventional Beta zeolite.
• Combination of these dual features provokes a remarkable catalytic activity in the epoxide rearrangement reactions.

Hierarchical Beta zeolites with enhanced accessibility obtained by crystallization of silanized zeolitic seeds were synthesized and investigated as catalysts for epoxide rearrangement reactions. On the other hand, hybrid zeolitic–mesoporous materials prepared from Beta protozeolitic units, and later assembled around cetyltrimethyl ammonium bromide (CTAB), were also synthesized for comparison purposes. Textural and structural properties were studied by N2 and Ar adsorption isotherms, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The coordination and stability of the Al atoms were investigated by 27Al MAS NMR. The acidic properties were analyzed by NH3 temperature programme desorption (TPD), and by FTIR probe pyridine adsorption–desorption to get insights on their acidic features and population of Brønsted and Lewis acidity. These zeolitic type materials featured additional porosity and enhanced textural properties compared with the conventional Beta zeolite and Al-MCM-41. Likewise, their acidic properties were modified, the distribution and strength of Brønsted and Lewis acid sites being different compared to the reference samples. These materials were tested in the liquid phase rearrangement of cyclic, branched, and linear epoxides with different sizes to explore how the acidity and the improved diffusion of the substrates through the channels influence their catalytic behaviour. In overall, hierarchical Beta zeolite exhibits the best combination of catalytic activity and selectivity due to enhanced accessibility and appropriate balance of Brønsted and Lewis acid sites. These results confirm that the hierarchical Beta zeolite is a potentially interesting catalyst for epoxide rearrangement reactions.